Electrical characterization of an interface n‐type conduction channel in cubic GaN/AlGaN heterostructures

Abstract

We report on the growth of non‐polar cubic GaN/AlxGa1‐xN heterostructures by plasma‐assisted molecular beam epitaxy on free standing (001) 3C‐SiC substrates. The samples consist of 600 nm thick GaN buffer and 30 nm AlxGa1‐xN layer. The growth was observed by in‐situ reflection high energy electron diffraction (RHEED). Layer thickness was determined by AlxGa1‐xN RHEED growth oscillations and by reflectance measurements after growth. The morphological and the structural properties are analyzed by high resolution x‐ray diffraction (HRXRD) and atomic force microscopy (AFM). Using a metal oxide semiconductor heterostructure (MOSH), capacitance voltage (CV) characteristics were measured. The oxide layer consists of SiO2, the thickness was varied between 15 nm and 30 nm. SiO2 layer was produced by plasma enhanced chemical vapour deposition (PECVD). The contact structure is lithographically deposited on top of the sample. Metal contacts have a diameter of 300 μm and were thermally evaporated consisting of 15 nm Ni and 50 nm Au. By CV measurements of the MOSH structures we obtain clear evidence for the existence of an electron accumulation layer at the GaN/AlGaN interface. The sheet carrier concentration at the hetero‐interface is calculated from experimental data (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Capacitance Voltage Characteristics and Electron Holography on Cubic AlGaN/GaN Heterojunctions

“…11) The N CV values measured at depths above 80 nm of 3 Â 10 17 cm À3 and at 20 nm of 2 Â 10 18 cm À3 , are attributed to the background carrier concentrations of cubic GaN and Al 0:3 Ga 0:7 N layers, respectively. These values are in good agreement with earlier C-V results measured on MOS structures 6) and on Schottky barrier devices 12) and are used in our simulations. The blue curve in Fig.…”

“…The structural properties of the samples were characterized by high-resolution X-ray diffraction (HRXRD) measurements. 6) From a reciprocal space map (RSM) of the grown sample around the asymmetric ( " 1 " 13) reflection we obtain the information that the 30 nm thick Al x Ga 1Àx N layer is pseudomorphic on the GaN buffer and that the aluminum mole fraction is 0.3, respectively.…”

Carbon doped asymmetric cubic AlN/GaN multi quantum well structures for high electrical isolation to 3C‐SiC substrates

“…Capacitance-voltage (C-V) measurements on cubic AlGaN/GaN metal-oxide-semiconductor (MOS) structures [12,13] and on Schottky diodes [14][15][16] showed in unintentially doped epilayers a background carrier concentration N D -N A of about 9x10 16 -2x10 17 cm -3 for the cubic GaN Table 1 and are used in our self-consistent band structure calculations. In Fig.…”

Free carrier accumulation at cubic AlGaN/GaN heterojunctions

“…16 The obtained electrical data are in good agreement (within a factor of two) with conventional C-V measurements on these cubic AlGaN/GaN heterostructures and MOS structures. 9,12,13 A positive curvature of the potential energy profile in the AlGaN region is also observed, indicating an ionized donor density which is not negligible. The electron holography measurement of the potential profile has an overall error of 15% in this experiment, mainly from the estimation of thickness and from residual diffraction contrast effects.…”